A. Field of the Invention
The present invention relates to compositions for improving lubrication and inhibiting corrosion in synthetic and semi-synthetic metalworking fluids. Most metal working fluids used today are water based and require the use of additives to yield the desired properties. In the present invention carboxylated amine fatty acid condensates have been found to demonstrate excellent lubrication and rust inhibition properties, with only moderate foaming. As additives, these novel compositions have been used with metalworking fluids and found to be effective lubricants and rust inhibitors with the potential to reduce metalworking costs by approximately one-half.
B. Description of the Prior Art
Two essential properties to an effective metalworking fluid are that it inhibits corrosion and provides adequate lubrication. These properties, however, are not inherently coexistent and are achieved by the use of special additives. Unfortunately, some additives are effective for only one of these purposes or cause excessive foaming.
For example, U.S. Pat. Nos. 4,239,635 (and Re. 30,885) to Rieder describes metal working compositions comprising a carboxylic acid group terminated polyoxyalkylene diamide, and the alkali metal, ammonium and organic amine salts of such diamides. Structurally, the compositions of Rieder can be distinguished from the present inventive composition by, among other points, the absence of a central amine group. As demonstrated in Table I, which follows, the composition of Rieder possesses adequate lubricating properties but does not have comparable rust inhibition characteristics when compared to the compositions of the present invention.
U.S. Pat. No. 4,344,861 to Levy discloses a method of inhibiting the corrosion of metals in contact with petroleum and petroleum fractions using bis-amides. The bis-amides are formed by reacting one or more polyamines with a dimer acid or with a dicarboxylic acid having from 2-12 carbon atoms. Although no specific dimer acids are listed, those produced by dimerizing fatty acids of 18 carbon atoms are stated to be of particular interest. Unlike the present invention, the composition disclosed in Levy is not shown to have any efficacious lubricating properties.
U.S. Pat. No. 3,801,609 to Magne discloses a lubricant comprising N,N-disubstitued fatty acid amines. Not only are there obvious structural differences between the present invention and the amines of Magne, the latter do not appear to possess effective corrosion inhibiting characteristics.
Finally, in an article by Ward, Jr. et al entitled "Industrial Utilization of C.sub.21, Dicarboxylic Acid" appearing at pages 219-224 in the July 1975 issue of Journal of the American Oil Chemists' Society, (Vol. 52), there are disclosed certain 21 carbon dicarboxylic acids having a plurality of industrial applications, including lubrication and corrosion inhibition. The article, however, does not disclose the carboxylated bis-amidoamines of the present invention.